Federal prosecutors, who have sought Chronicle reporters' sources of secret grand jury testimony about steroids use by athletes, expanded their demands last month to include the confidential sources for hundreds of articles about the BALCO drug investigation, lawyers for the newspaper said Wednesday.

"The government's fishing expedition cannot be countenanced," attorneys for the Hearst Corp., which owns The Chronicle, declared in papers filed with a federal judge.

They sought to dismiss a Justice Department subpoena seeking documents that would identify sources for the articles, or to obtain an order that would prohibit the government from inquiring into The Chronicle's sources for its reporting about the case.

Thom Mrozek, spokesman for the U.S. attorney's office in Los Angeles, declined comment, saying prosecutors would reply in writing at a later date.

The case arose from a federal grand jury investigation of the Bay Area Laboratory Co-Operative, or BALCO, and its supplying of performance-enhancing drugs to professional athletes.

This May, the newspaper and reporters Mark Fainaru-Wada and Lance Williams received subpoenas from a new grand jury demanding their sources of the BALCO grand jury testimony and any documents that would reveal the sources.

U.S. District Judge Jeffrey White ruled Aug. 15 that the reporters must identify their sources, saying neither the Constitution nor federal law allows journalists to withhold information from a grand jury. Prosecutors agreed Tuesday to delay imprisonment of the reporters for contempt of court until the Ninth U.S. Circuit Court of Appeals in San Francisco rules on their appeal of White's decision.

In Wednesday's filing, Hearst lawyers said prosecutors changed the scope of their inquiry Aug. 3, in a conversation with attorneys for the newspaper. Until then, they said, prosecutors had sought only documents that would identify the leaker of the grand jury transcripts, and were repeatedly told by The Chronicle that it had no such documents.

But on Aug. 3, prosecutors said the subpoena that had been issued three months earlier required the newspaper to produce "any documents (broadly defined) that reflected any information about any grand jury testimony in the BALCO investigation," attorney David Shapiro said in a court declaration.

By its new interpretation, the government is now seeking documents, such as e-mails, that would identify confidential sources for all BALCO-related articles, even those that had nothing to do with grand jury transcripts, Hearst lawyers said. They said The Chronicle has published about 450 such articles, including 150 by Fainaru-Wada and Williams.

"The information now sought has only a remote and tenuous connection to the government's investigation" of the leaks, and would have a "wide and unprecedented impact ... on Chronicle reporters' confidential source relationships," the lawyers said.

Attorneys for the two reporters filed a separate motion Wednesday asking White to clarify that his Aug. 15 order referred only to testimony about sources of the grand jury transcripts.